Technical Abstract:
Effect of genetic variation on chickens' susceptibility to stress and infection were examined in the study. Sixty chicks at 3- wk-age from each of the three genetic lines, i.e., commercial Dektal XL (DXL), HGPS, and LGPS, were used. The HGPS and LGPS lines were genetically selected based on high or low productivity and survivability in colony cages. 5.0 mg/kg of lipopolysaccharide (LPS) was injected intravenously. Samples were collected from sham controls and chicks at 6, 12, 24, 48, and 72 hr post-injection (PI), respectively. Although a similar pattern of temperature change was found immediately following the injection among the genetic lines, the pattern was different in its speed of return to the control levels, which was in the order, HGPS> DXL>LGPS. LPS-induced body weight loss was found in DXL and HGPS chicks at 6 hr (P<0.05) and 24 hr (P<0.01) PI, respectively, but, in LGPS chicks, it did not return to the control levels until 48 hr PI (P<0.05). LPS-induced increase in the relative weight of the liver and heart were found only in LGPS chicks from 12 to 48 hr (P<0.01) and from 6 to 72 hr PI (t test, P<0.05), respectively. The spleens became heavier (P<0.05) in the chicks from all the three lines at 72 hr PI, which was in the order, HGPS>DXL>LGPS. Adrenal glands were heavier in LGPS chicks at 6 hr PI (t test, P<0.05). However, increased plasma concentrations of corticosterone were found only in the DXL chicks at 6 and 12 hr PI (t test, P<0.05). The study showed that differential physiological responses to LPS injection in chickens are strain and organ specific. The differences may reflect each line's unique adaptability to stress and resistance to infection.